Acquired syphilis^[1]

• Primary syphilis: incubation period 2-3 weeks (range 9-90 days): local infection.
• Secondary syphilis: incubation period 6-12 weeks (range 1-6 months): generalised infection.
• Early latent syphilis: asymptomatic syphilis of less than 2 years' duration.
• Late latent syphilis: asymptomatic syphilis of 2 years' duration or longer.
• Late symptomatic syphilis (tertiary syphilis): cardiovascular syphilis, neurosyphilis, gummatous syphilis.

Congenital syphilis

• Early congenital syphilis occurs within the first 2 years of life.
• Late congenital syphilis emerges in children older than 2 years.

Epidemiology

• In 2003, there were 1,580 cases diagnosed in sexually transmitted disease (STD) clinics in England, Wales and Northern Ireland. The highest rates of syphilis are seen in women aged 20-24 and men aged 25-34 years.^[2]
• More recently there were 3,762 diagnoses of infectious syphilis in 2007.^[3]
• Epidemics of infectious syphilis are occurring especially among men who have sex with men (accounting for over 70% of cases) and there is a strong relationship with co-infection with HIV.^[3]
• The tertiary stage is now rarely seen in the UK, possibly because those affected many years ago have received antibiotics for other infections in the intervening time.^[4]
• There is also an increase in congenital syphilis cases as a result of increased incidence of syphilis in women of reproductive age.^[3]

Presentation

Primary syphilis

• Primary lesion develops at the site of infection, which heals in 2-6 weeks.
• Small, painless papule that rapidly forms an ulcer (the chancre). The chancre is usually single, round or oval, painless, surrounded by a bright red margin and indurated with a clean base, and discharging clear serum.
• Chancres may be atypical, eg multiple, painful, purulent, destructive and may be extragenital.
• They are usually found in heterosexual men on the coronary sulcus, the glans and inner surface of the prepuce but may appear on the shaft and beyond. In homosexual men, they are usually found in the anal canal and, less frequently, in the mouth and genitalia. In women, they are found on the vulva, labia and, much less frequently, on the cervix.
• Extragenital sites are the lips, mouth, buttocks and fingers.
• Enlarged regional lymph nodes that are painless, discrete, firm and not fixed to surrounding tissues.

Secondary syphilis

• Secondary syphilis often appears 6 weeks after the beginning of the primary lesion but may overlap or not appear for several months.
• Multisystem involvement occurs within the first two years of infection.
• Systemic symptoms are mild or absent, but include night-time headaches, malaise, slight fever and aches.
• A generalised polymorphic rash often affects the palms, soles and face. The rash is classically non-itchy but may be itchy, especially in dark-skinned patients. It is associated with generalised painless lymphadenopathy.
• Papules enlarge into condylomata lata (pink or grey discs) in moist warm areas. Papule lesions disappear spontaneously.
• There may also be mucocutaneous lesions.
• Less common presentations include patchy alopecia, anterior uveitis, meningitis, cranial nerve palsies, hepatitis, splenomegaly, periostitis and glomerulonephritis.
• In 80% of cases, patients enter the latent asymptomatic stage which for over half of them persists for life. In about 20% of patients, an infectious relapse occurs during the next year.

Early latent syphilis

• Characterised by positive serological tests for syphilis with no clinical evidence of treponemal infection within the first two years of infection.

Late latent syphilis

• Infection of more than two years' duration diagnosed on serological testing with no symptoms or signs of late manifestations of syphilis.
• Studies of cohorts of untreated patients suggest that symptomatic late syphilis is found in up to 40% of individuals with late T. pallidum infection.

Tertiary syphilis

This consists of three major clinical manifestations, which may coexist:

• Neurological syphilis:
  • Asymptomatic neurosyphilis: late syphilis with abnormal cerebrospinal fluid (CSF) examination but with no associated neurological symptoms or signs.
  • Symptomatic neurosyphilis: the most common presentations are dorsal column loss (tabes dorsalis), dementia (general paralysis of the insane) and meningovascular involvement.
• Cardiovascular syphilis:
  • Characterised by an aortitis, which usually involves the aortic root but may affect other parts of the aorta, usually spreading distally from the aortic root.
  • The most frequent clinical manifestations are aortic regurgitation, aortic aneurysm and angina.
• Gummata:
  • Inflammatory fibrous nodules or plaques, which may be locally destructive.
  • Can occur in any organ but most commonly affect bone and skin.

Differential diagnosis

Primary syphilis

Differentials of chancre include:

• Herpetic ulcers (especially chronic mucocutaneous anogenital herpes occurring with HIV infection).
• Chancroid.
• Lymphogranuloma venereum.
• Donovanosis.

Secondary syphilis

Differentials of the rash include:

• Pityriasis rosea
• Viral exanthema

Tertiary syphilis

As the presentation is variable so the differential diagnoses are extensive but syphilis should be considered in anyone presenting with cardiac or neurological signs or symptoms. The history and examination should help guide the likelihood of tertiary syphilis as a cause.

Investigations^[1]

Investigations must include a screen for all sexually transmitted infections as well as investigation for other possible diagnoses. All patients with neurological signs or symptoms and those who fail treatment should have a lumbar puncture. Similarly, cardiac investigations may also be indicated, eg ECG and ECHO.

Specific treponemal tests include^[4]

• Treponemal enzyme immunoassay (EIA) - can be for immunoglobulin M (IgM) for early infection or immunoglobulin G (IgG) (the latter becomes positive at 5 weeks) or both. Check both for screening.
• T. pallidum chemiluminescent assay.
• T. pallidum haemagglutination assay (TPHA).
• T. pallidum particle agglutination assay (TPPA).
• Fluorescent treponemal antibody absorbed test (FTA-abs).
• T. pallidum recombinant antigen line immunoassay.

All of the above tests can be used for screening but the recommendations are to request EIA IgM for primary syphilis.^[4] All of these will also be positive in secondary and early latent syphilis. They will also be unable to differentiate between other treponemal diseases, eg yaws. All positive tests should then be confirmed by using different test.^[4]

Cardiolipin or non-treponemal tests^[4]

• Venereal disease reference laboratory (VDRL) or rapid plasmin reagin (RPR) - quantitative VDRL can be used as an indication of the stage of syphilis and is also used for monitoring treatment.^[5]
• Provides a titre, thus an indication of disease activity.
• Perform VDRL/RPR when treponemal tests are positive.
• False-negatives may occur in secondary or early latent syphilis - thus may need to repeat.

Demonstration of T. pallidum

• From lesions or infected lymph nodes in early syphilis.
• Dark field microscopy.
• Direct fluorescent antibody (DFA) test.
• Polymerase chain reaction (PCR).

Management

• Treatment should be within an STD clinic with enquiries about sexual contacts.
• Patients who acquire syphilis are at significant risk of reinfection, and should therefore be regularly screened for syphilis and given sexual health promotion. All patients should be offered screening for other sexually transmitted infections, including HIV.

Drugs

Recommended regimes for adults:^[1]

• Primary, secondary, early latent syphilis: benzathine penicillin 2.4 mega units (intramuscular (IM), single dose) is first-line and oral azithromycin single dose is second-line.^[4] Azithromycin has been shown to be as effective in treating early syphilis as benzathine penicillin.^[6] Alternatives that have been used include procaine penicillin 600,000 units (IM, once daily for 10 days) or doxycycline 100 mg twice daily for 14 days.
• Late latent syphilis: benzathine penicillin weekly for three weeks is first-line; the exception being neurosyphilis where procaine penicillin with oral probenecid remains first-line.
• Neurosyphilis: procaine penicillin 2.4 units once daily (IM, for 17 days) with oral probenecid 500 mg four times a day. Alternatively, doxycycline 200 mg twice daily for 28 days.
• Pregnancy:
  • Treatment depends upon which trimester the presentation is in: first and second trimesters: give single dose benzathine penicillin; third trimester two doses of benzathine penicillin one week apart. For late syphilis treat as for nonpregnant (avoiding tetracyclines). Alternatives include ceftriaxone 500 mg IM for 10 days.^[4]

Jarisch-Herxheimer reaction

• Is a reaction to treatment.^[4]
• An acute febrile illness with headache, myalgia, chills and rigors and resolving within 24 hours.
• Common in early syphilis but is usually not important unless there is neurological or ophthalmic involvement or in pregnancy when it may cause fetal distress and premature labour.
• It is uncommon in late syphilis but may be life-threatening.
• Treatment is with prednisolone and antipyretics.

Prevention of syphilis

• Treatment of asymptomatic contacts
• Use of condoms

Intrauterine syphilis

• In pregnant women with untreated early syphilis, 70-100% of infants will be infected, with stillbirths in up to one third of cases.^[4]
• Diagnosis:
  • Early (first two years): rash including condylomata lata, vesiculobullous lesions, snuffles, haemorrhagic rhinitis, osteochondritis, periostitis, pseudoparalysis, mucous patches, perioral fissures, hepatosplenomegaly, generalised lymphadenopathy, glomerulonephritis, neurological or ocular involvement, haemolysis, thrombocytopenia.
  • Late, including stigmata: interstitial keratitis, Clutton's joints (arthritis of the knees), Hutchinson's incisors, mulberry molars, high palatal arch, rhagades, deafness, frontal bossing, short maxilla, protuberance of mandible, saddle nose deformity, sternoclavicular thickening, paroxysmal cold haemoglobinuria, neurological or gummatous involvement.
• Investigations:
  • Serological tests that detect IgG may be positive due to passive transfer of maternal antibodies.^[7]
  • A positive anti-treponemal EIA IgM is indicative of congenital infection.
  • Serological tests may be negative in infants infected in late pregnancy and should be repeated.
• Treatment:
  • Refer all pregnant women with syphilis to fetal medicine specialists.^[4]
  • Intravenous benzyl penicillin for the first ten days of life.
  • Older siblings should be screened for congenital syphilis.
  • Congenital syphilis diagnosed in an older child or in adulthood should be managed as for late syphilis.
  • Parents, all siblings and any sexual partner should be screened for syphilis.